Introduction to Gas Technology
TABLE OF CONTENTS
Section One Glossary of Terms
Section Two Symbols
Section Three Units of Measurements
Section Four Physical Properties of Hydrocarbon Systems
Section Six Gas Dew Point Reduction
Section Seven Hydrate Formation and Prevention
Section Eight Typical Gas Processes
Section Nine Rules of Thumb
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SECTION ONE
GLOSSARY OF
TERMS
In order to have a fundamental understanding of gas processing, it is necessary to learn some basic terminology. The following Glossary contains sufficient relative terms for a gas production operator to begin to understand gas production equipment and principles of operation.
Absorption
The process by which one fluid substance draws into itself another fluid substance. For example, gas dehydration, glycol-absorbing moisture from wet gas.
Absorption Tower
A tower or column which effects contact between a rising gas stream and a falling
liquid so that part of the gas may betaken up by the liquid. Also known as a Contactor.
Accumulator
A vessel for the temporary storage of a gas or liquid; usually used for collecting sufficient material for a continuous charge to some downstream treatment process.
Glossary of Terms
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Acid
A member of an important and fundamental category of chemical substances haracterized by having available reactive hydrogen and requiring an alkali to neutralize it. It usually has a sour, like vinegar, which is in fact a dilute solution of acetic acid.
Acid Gas
Hydrogen sulphide and carbon dioxide, both of which are acidic when dissolved
in water.
Adsorption
Describes any process, where in molecules of the gas are held on the surface of the solid, by surface forces.
Additives
Substances which, when added to petroleum fractions, modify or enhance their natural properties.
Air
Air contains approximately by volume 78 - 79% nitrogen; 20.95% oxygen; 0.94%
argon; traces of carbon dioxide, helium, etc.
Aliphatic Hydrocarbons
Hydrocarbons in which the carbonhydrogen groupings are arranged in open chains which may be branched.
Alkali
In chemistry, any substance having marked basic properties. In its restricted and common sense, the term is applied only to hydroxides of potassium, sodium, lithium and ammonium. They are soluble in water; have the power of neutralising and forming salts with acids.
Alkalis will also turn red litmus blue. An example, is sodium hydroxide.
Ambient Air
The air surrounding equipment or in a certain area.
Analysis
The process of determining thecomposition of a substance by chemical or physical methods.
Anti-Foam Agent A specific chemical agent used for combating and destroying a particular type of foam. Addition of anti-foam to soap suds will cause the soap bubbles to collapse.
API Gravity API An arbitrary scale expressing the gravity or density of liquid petroleum products.
The measuring scale is calibrated in terms of API degrees.
Aqueous
Watery; of, pertaining to, or containing water.
Aromatics
A group of hydrocarbons, of which benzene is the parent. They are called "aromatics" because many of their derivatives have sweet or aromatic odours. These hydrocarbons are of relatively high specific gravity and possess good solvent properties.
Typical aromatics are: benzene, toluene, xylene.
Atmosphere
Is the mixture of gases and water vapour
surrounding the earth.
Atmospheric Pressure
The pressure of air at sea level exerted equally in all directions. The standard pressure is that under which the mercury barometer stands at 760 mm or 30 inches. It is equivalent to about 14.7 psia
Atom
The smallest complete particle of an
element, which can be obtained, yet,
which retains all physical and chemical
properties of the element.
Glossary of Terms
Atomic Weight
The weight of an elementary atom in relation to the weight of an atom of hydrogen, a hydrogen atom being taken as 1.008. The proportional weights based on hydrogen, of all known elemental atoms have been accurately determined by direct experiment. This
arbitrary system permits the calculation of the proportionate quantities of the elements composing one molecule of any compound. The weight of the molecule is the sum of the weights of the atoms forming that molecule or chemical compound.
Back-Pressure Regulator
An automatic valve designed to maintain a constant back pressure in the discharge line of a vessel.
Baffle
A partial restriction, generally a plate located to change the direction, guide the flow, or promotes mixing within the equipment in which it is installed.
Barrel
As the standard unit of measurement of liquids in the petroleum industry, it contains 42 U.S. Standard gallons, and 35 English gallons.
Base
A compound which reacts with an acid to
form a salt. (See 'Alkali')
Benzene
A pure aromatic hydrocarbon of characteristic odour.
Bleeding
Diverting from a line or vessel a small portion of the contained material usually accomplished by slightly "cracking" a valve on the line or vessel.
Boiling
The process by which a liquid is rapidly changed to vapour by the application of heat. Molecules vaporizing in a liquid and at the surface-causing interior bubble formation.
Boiling Point
The temperature at which a substance begins to boil or to be converted into vapour by bubbles forming within its mass. It varies with the applied pressure.
Boiling Range
The range of temperature usually determined at atmospheric pressure in standard laboratory apparatus, over which the boiling of an oil or condensate commences, proceeds and finishes.
Bomb
A steel cylinder used as a testing device for conducting oil or gas tests under high pressure. Used for tests, such as sulphur content, and vapour pressure (Reid Vapour Pressure).
Bottoms
The liquid which collects in the base or bottom of a vessel or tank.
Bottom-Hole Differential Pressure
(BHDP):
The difference between the reservoir pressure and the pressure at the bottom of a producing well is known as the bhdp.
The magnitude of this pressure difference determines the rate of flow of fluid towards the well bore.
Bottom Settlings
Sludge collected at the bottom of vessels or tanks, which comprises an emulsified mixture of oil and water and sometimes wax, asphalt and mud.
Breathing
The movement of gas (hydrocarbon vapours or air) in and out of the vent lines of storage tanks due to alternate heating and cooling.
Brine
Water, which is nearly saturated with, salts.
Basic Sediments and Water (BS&W)
This comprises the solids and aqueous solutions which may be present in oil and which are separable by means of gravity or centrifuge.
British Thermal Unit (Btu)
The heat required to raise the temperature of 1 lb of water through 1 F.
Bubble Cap
An inverted cup with a notched or slotted periphery to disperse the vapour in small bubbles beneath the surface of the liquid on the bubble' plate in a Contactor, or stabilizer column.
Bubble Point
The temperature at which the first incipient vaporization of a liquid occurs from a liquid mixture. It corresponds with the equilibrium point of zero per cent vaporization or 100 per cent condensation. The pressure should be specified if not one atmosphere.
Bubble Tower or Column
A fractionating or stabilizing column so constructed that the rising vapours pass through layers of condensate on a series of plates or trays. The vapour passes from one tray to the next above by bubbling under one or more caps and aut through the liquid on the tray. The less volatile components of vapour condense in bubbling through the liquid on the tray,
and overflow to the next lower tray, and ultimately back into the reboiler.
Butane
Commercial butane is a mixture of gaseous alkanes, mainly normal-butane and iso-butane. When blended into gasoline in small quantities it improves volatility and octane number. Butane can be stored under pressure as a liquid at atmospheric temperatures and as
"bottled gas" it is widely used for domestic heating and cooking.
Calibration
1. The graduation of a measuring instrument 2. The determination of error in a measuring instrument.
Calorie
The amount of heat required to raise the temperature of 1 gram of water through 1oC. The kilogram calorie (i.e. 1000 calories or 3.97 Btu) is also employed.
Calorific Value
The amount of heat obtained by the complete combustion of unit weight of fuel. It is normally expressed as calories per gram or Btu per pound. The gross calorific value represents the total amount of heat of combustion. This total includes the latent heat of condensation of the water vapour produced by the combustion. Due to the fact that the water vapour is not usually condensed under practical conditions of combustion, the "lower" or net calorific value, which excludes the latent heat of condensation of the water vapour, is a better guide to the amount of useful heat obtainable from the fuel.
Capillarity
The rising or falling of the surface of a liquid in contact with a solid. The fluid actually rises above the normal level due to surface tension.
Carbon Dioxide
A heavy, colourless gas, (Co ) which will not support combustion. Dissolved in water, it forms carbonic acid.
Carbon Monoxide
A colourless, odourless gas (CO) a product resulting from the incomplete combustion of carbon.
Combustion
Chemically, it is a process of rapid oxidation caused by the union of the oxygen of the air, the supporter of combustion with any material, which is
capable of oxidation.
Compound
A substance formed by the combination of two or more components in definite proportions by weight, and possessing physical and chemical properties entirely different from those of the components.
Condensate (Hydrocarbon
Condensate)
Refers to liquifiable hydrocarbons that have condensed from natural gas.
Condensation
In physics and engineering the act or process of changing a vapour to a liquid, or a lighter fluid to another and denser form, by depression of temperature or
increase of pressure.
Condenser
As ordinarily used, the term refers to heat exchangers used for cooling and liquefying hydrocarbon vapours.
Conduction
The transfer of heat through a solid or fluids by direct contact of particles.
Convection
The flow of heat through liquids or gases by actual mixing of the liquids or gases
(physical turbulence).
Coolers
Any type of heat exchanger whose primary function is to reduce the temperature of one of the passing fluids by heat transfer to the other.
Corrosion
Destructive alteration of metal from chemical reactions.
Covalence
The term used to indicate the bonding that results from the mutual sharing of pairs of electrons.
Critical Pressure
The pressure necessary to condense a gas at the critical temperature above which the gas cannot be liquefied, no matter what pressure is applied.
Critical Temperature
The temperature at which a gas can be liquefied by a maximum pressure, the critical pressure; above this temperature the gas cannot be liquefied, no matter what pressure is applied.
Crude Oil
See 'Petroleum'.
Cycling
The injection of dry gas into a gas condensate reservoir at such points that it will push or sweep the gas condensate towards the producing well.
Decline
The decrease in yields of a gas or oil .well.
Decomposition ا
The breaking up of compounds into smaller chemical forms, through the application of heat, change in other physical conditions, or through the introduction of other chemical bodies.
Dehydrate
To render free from water.
Dew Point
The temperature at which vapour starts
to condense.
Disposal Well
A well into which salt water from producing wells is discharged.
Downstream
The portion of a flow that has passed a given point.
Dry Gas
A gas which does not contain water or heavier fractions which may easily condense under normal atmospheric temperatures.
Emulsion
A liquid mixture in which oil in minute globules is suspended in water or water in tiny droplets is suspended in oil.
Enthalpy
The heat content per unit mass expressed in Btu per lb.
Entrainment or Carryover
Relatively non-volatile contaminating material which is carried over by the "overhead" effluent from a separator, stabilizer column or an absorber. This may be as liquid droplets or finely divided solids suspended in a gas, a vapour or in a discrete liquid.
Ethane
A hydrocarbon of the alkane series (C H ). It boils at -128.2oF at atmospheric pressure.
Evaporation
The conversion of a liquid into a vapour, usually by means of heat.
Exothermic
Relating to or designating a reaction, which occurs with the evolution of heat, so that the temperature of the reacting bodies is raised.
Explosive Limits
The limits of percentage composition of mixtures of gases and air within which an explosion takes place when the mixture is ignited. The lower limit of flammability corresponds to the minimum amount of combustible gas, which must be present to support combustion and the upper limit to the maximum amount of combustible gas, which can be present and still permit combustion of the mixture.
Firetube
A U-tube or hairpin installed inside an indirect fired heater with a burner located at the inlet end and a stack at the outlet.
Also known as a combustion tube.
Flare Gas
Gas diverted to flare tips, stacks or pits to be burned.
Flash
When vapours rise suddenly from a liquid they are said to "flash". Lowering the pressure on a liquid, with heat or without heat having been applied, may induce flashing. Primary stage of
separation.
Flash Production
The first yield from a well.
Flue
A channel or passageway for smoke, waste gases, etc. As subsidiary tube or smoke duct in a chimney, or a tube carrying gases of combustion in a boiler or Firetube.
Fluid
A body made up of particles which easily change their relative position without separation of the mass, and which yield easily to pressure. The term applies to any body capable of flowing whether liquid or gaseous.
Fraction
Any derivative separated by distillation from petroleum.
Fractionating Column
A tall, cylindrical steel tower divided into sections by trays having specially dedesigned perforations surmounted by
Basic Safety
The safety
policies and regulation laid down by
Equipment safety
All equipment must be maintained and inspected at regulars interval to ensure that Company Safety Standard are met and complied with.
When defects are found they must be reported immediately to the shift Production Supervisor, who where necessary will ensure that the defective equipment is not used until a work order is raised and the equipment has been serviced/repaired and checked by a delegated person.
Personnel Safety
Personnel will ensure that they are suitably equipped with personal safety equipment and any additional equipment that may be required for the task to be carried out.
It is mandatory for safety glasses, safety helmets and safety boots to be worn outside the accommodation
Main Hazard
The three main hazards associated with this system are:
Hydrocarbons
Hydrogen Sulphide (H2S)
Ingress of Oxygen (O2)
The Flare System has the potential to be dangerous due to activities involving high and low pressure inflammable hydrocarbon gases.
H2S and CO2 waste gases are present in the Flare System inventory. This includes the flare headers, knockout vessels, flare boom, HP Flare Tip 60-230-FC-101, and LP Flare Tip 60-230-FC-102
In order to avoid the potential hazard of oxygen ingress into HP/LP flare tip, a continual fuel gas purge must be maintained at the remote ends of the flare headers. The specific safety consideration is that a failure of the fuel gas purge could possibly result in a potentially explosive mixture of oxygen and hydrocarbon gases in the Flare System.
Hydrogen sulphide
H2S is present within any hydrocarbon gas entrained in the Flare and Vent System.
Hydrogen sulphide is highly poisonous gas capable of producing instant death when inhaled even in relatively small concentrations. A concentration as small as 10 parts per million by volume is the limit for safe exposure for an eight hour working day. Concentrations of only 600 parts per million are fatal in thirty minutes.
Maintenance
Vessel or equipment must be properly drained and purged before breaking into any pipework or equipment.
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